Re: [Boost-users] BOOST_ALL_DYN_LINK

Subject: Re: [Boost-users] BOOST_ALL_DYN_LINK
From: Vladimir Prus (ghost_at_[hidden])
Date: 2010-03-08 11:43:07

Paul wrote:

>      > Then, if I define BOOST_ALL_DYN_LINK, I get lots of these messages:
>      >
>      > boost_1_42_0\boost/signals/detail/signal_base.hpp(113) : warning
>     C4251:
>      > 'boost::signals::detail::signal_base_impl::combiner_' : class
>     'boost::any'
>      > needs to have dll-interface to be used by clients of class
>      > 'boost::signals::detail::signal_base_impl'
>      > 39>        boost_1_42_0\boost/any.hpp(36) : see declaration of
>     'boost::any'
>      >
>      > I've read up on this and understand why the warnings are shown.
>      >
>      > BUT,
>      > I don't understand why I am able to still link my program if I do
>     NOT define
>      > BOOST_ALL_DYN_LINK.
>      >
>      > Without the flag, it compiles without warnings, it links without
>     problems,
>      > AND the executable requires the signals DLL to be available, so
>     clearly it
>      > IS dynamically linked.  Right?
> 
>     Do you include import library for Boost.Signals in the link? Then,
>     presumably,
>     compiler automatically 'dllimports' the symbol. Please see:
> 
>            http://blogs.msdn.com/oldnewthing/archive/2006/07/26/679044.aspx
> 
>     Does this help?
> 
>     - Volodya
> 
> 
> This DOES help a lot !
> 
> So, I have a few options:
> 
> 1) Define BOOST_ALL_DYN_LINK and put up with the excess warnings.
>    This would be ok if the boost developers could "fix" their headers by 
> adding #pragmas to hide the warnings when they know its not a problem.
> 
> 2) Define BOOST_ALL_DYN_LINK and write a couple of header files that 
> wrap the boost headers with #pragmas (eg especially for boost::signals)
> 
> 3) Do not define BOOST_ALL_DYN_LINK, and allow Windows the link "the 
> naive way", which might give slower performance, but maybe not.

It would certainly help if somebody with practical experience with Windows
comment here (which I am not). For all I understand, that warning is false
positive, given that boost::any is all templated code, and probably the
best solution is to disable it in your project settings -- and, maybe,
when building boost itself? Comments?

- Volodya